Distinguishing between short-lived reactive oxygen species like hydroxyl and superoxide radicals is difficult; the most successful approaches employ electron spin resonance (ESR) spin-trapping techniques. Using the spin trap 5,5-dimethyl-l-pyrroline N-oxide (DMPO) to selectively trap various radicals in the presence and absence of ethanol, an HPLC system which is capable of separating the hydroxyl- and superoxide-generated DMPO adduct species has been developed. The radical-generated DMPO adducts were measured with an electrochemical detector attached to the HPLC system and confirmed by spin-trapping techniques. The HPLC separation was carried out on an ODS reverse-phase column with a pH 5.1 buffered 8.5% acetonitrile mobile phase. The advantage of the HPLC system described is that it permits the separation and detection of hydroxyl and superoxide radicals without requiring ESR instrumentation. The antineoplastic bioreductive alkylating agent mitomycin C, when activated by NADPH-cytochrome c reductase, was shown to generate both hydroxyl and superoxide radicals.